LC/DAD/MS' and ICP-AES Assay and Correlations between Phenolic Compounds and Toxic Metals in Endemic Thymus alsarensis from the Thallium Enriched Allchar Locality

摘要

Samples of Thymus alsarensis Ronniger, an endemic species for the Allchar locality, were evaluated for their polyphenolic composition and heavy metals. Allchar district is an abandoned antimony-arsenic-thallium deposit in the north-west of Kozuf Mountain, R. Macedonia, with a unique mineral composition affecting the mineral composition of the flora. A systematic method for phenolic compounds characterization was developed using mass spectrometry coupled to HPLC/DAD. Analyses were focused on the polyphenolic compounds to establish a possible correlation to the region specific heavy metals As and T1 in the different organs of T. alsarensis. Twenty-seven polyphenols: phenolic acid derivatives and fiavonoid glycosides of luteolin, apigenin, quercetin, and kaempferol were detected; contents were higher in the leaves and flowers compared with stems and roots. Quinic acid (1), prolithospermic acid (6), salvianolic acid B (7), salvianolic acid A (8), monomethyl lithospermate (9), luteolin dihexoside (12), luteolin pentosyl-hexoside (14), luteolin acetyl pentosyl-hexoside (16), luteolin acetyl hexoside (17), luteolin dipentoside (21), luteolin pentoside (24), luteolin acetyl dipentoside (25), kaempferol pentosyl-hexoside (19) and kaempferol acetyl pentosyl-hexoside (22) were detected in T. alsarensis for the first time. To assay the content of As and T1, root, stem, leaf and flower samples were analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES). Significant accumulation of As and Tl was observed with As content from 0.25 to 140 mg/kg and Tl from 0.10 to 496 mg/kg. The content of As was much higher in the roots, while the content of Tl was significantly higher in the roots, flowers and leaves in all T. alsarensis specimens. Comparison of the results obtained for total polyphenols and for As and Tl content does not suggest any correlation (positive or negative) between the total phenolic content and the content of T1 and As. On the other hand, it is evident that the soil rich with specific heavy metals (T1 and As) affects the type of polyphenolic compounds produced in different organs, compared with other Thymus species growing on soil that is not contaminated.